The growing trend could mean roughly 1,000 chimps in the
U.S. used for research or warehoused for many years in laboratory cages could
be "retired" to sanctuaries by around 2020.

That's according to Kathleen Conlee of the Humane Society of
the United States, which seven years ago began urging companies to phase out
all chimp research.

The trend is driven by improved technology, animal
alternatives and pressure from animal rights groups, the National Institutes of
Health and Congress.

Last June, reacting to an Institute of Medicine study
Congress had requested that concluded nearly all chimp research is unnecessary,
the NIH announced it would retire and send about 90 percent of government-owned
research chimps to the Chimp Haven sanctuary in Keithville, La. It's now home
to about 160 chimps, with nearly 60 more to arrive soon.

After several years, the NIH plans to decide whether the
remaining chimps in government labs can also be moved to sanctuaries. Roughly
450 other chimps are owned by private labs that do research under contract for
drug makers and other companies.

"It's been a long road in trying to end the use of
chimpanzees in research, and we're now at a turning point," Conlee told
The Associated Press Thursday. "We're going to keep on (advocating) until
the chimpanzees in laboratories are all in sanctuaries."

Merck spokeswoman Caroline Lappetito said the company, based
in Whitehouse Station, N.J., decided late last year to stop research on
chimpanzees and switch to alternative types of testing.

"The science has advanced, and we don't really need
it," Lappetito said.

Merck, the world's third-biggest drug maker, is the largest
to make the switch.

Companies that develop medicines and consumer products such
as cosmetics have long used animals to test safety and effectiveness. In the
case of experimental medicines, drugmakers must test on animals before the Food
and Drug Administration will let them do the human testing needed for approval
of a new therapy.

Nearly all animal experiments in the U.S. involve mice, rats
and guinea pigs, although some are done on dogs and great apes, almost always
chimpanzees.

But animal research, particularly on primates and pet
species such as dogs and rabbits, has long drawn criticism from animal rights
groups, including protests outside laboratories and at annual shareholder
meetings. Besides calling the practice inhumane, activists often have alleged -
and sometimes proven - that animals were being abused.

Many companies previously said it was necessary to test
potential medicines and vaccines on nonhuman primates because they needed an
animal in which the anatomy and disease course were very similar to that in
humans.

That thinking changed as technology allowed researchers to
do initial testing via computer simulations, in bacteria or cells, and in
animals as small as fish. Many drug makers also found ways to do testing on far
fewer animals and to limit the discomfort of experiments by using painkillers
and tranquilizers. And many of the companies pledging not to use chimps in the
future never did so.

British drugmaker GlaxoSmithKline PLC was one of the first
to stop research in chimps, back in 2008.

"Research we did on nonhuman primates was kept to a
minimum" even before that, said spokeswoman Melinda Stubee.

Because chimpanzees used for commercial medical research
generally are confined in the labs of contract testing companies, Conlee said
the Humane Society is trying to convince them that there's no longer enough
demand to continue warehousing chimpanzees for potential future work. She hopes
they'll pay to support those chimpanzees in one of five U.S. accredited
sanctuaries for former research chimps.